1. Field of the Invention
The present invention relates to a diaphragm using a substantially filmy base material that is formed by a plurality of linear members and a speaker.
2. Description of Related Art
There has been conventionally known a diaphragm used for a speaker or the like, which employs a so-called triaxial fabric woven by a first, second and third linear members that cross with each other at, for instance, an angle of about 60° (see, for instance, Document 1: Japanese Patent Publication No. 2681991, left column of page 2 to right column of page 3, Document 2: JP-A-2002-78077, right column of page 3, Document 3: JP-A-8-47083, right column of page 2, and Document 4: JP-A-5-284594, right column of page 2).
Document 1 discloses an arrangement in which a prepreg prepared by impregnating a triaxial fabric with a thermosetting resin is placed on a cavity plate having a desired shape. Then, a core is placed on the prepreg to perform compression, heating for setting the resin, and mold the prepreg.
Document 2 discloses a three-layer structure including: a honeycomb core material obtained by forming an aramid fiber material into a honeycomb core; and triaxial fabrics adhered to both sides of the honeycomb core material.
Document 3 discloses an arrangement in which a triaxial fabric as a base material is coated with a phenol resin and a chlorosulfonated polyethylene resin. The base material is then molded with predetermined molding temperature and molding time to have a semicircular cross section.
Document 4 discloses an arrangement in which a triaxial fabric is used as a surround material of a diaphragm, the surround material being coated with a phenol resin and a chlorosulfonated polyethylene resin. The surround material is then heated, molded and cut into a predetermined shape to obtain a surround, the inner side of which is bonded to a diaphragm body.
However, with the arrangements disclosed in Documents 1 through 4, since tensile strength is substantially the same only in three directions as axial directions of the linear members, i.e., 0°, 60° and 120°, tensile strength in a direction of, for instance, 30° might be lower than those of the three directions described above. The difference of the tensile strengths generates deformation of the diaphragm such as bending that causes degradation of sound quality, which might cause music or the like to be output with sound quality different from the original one.